A wide variety of products such as feed pellets, tablets, tool inserts, electronic components and automobile parts are produced by pouring a fixed mass or volume of dry cohesive particulate material into a die and subjecting the material to high pressures. This manufacturing technique is referred to as compaction or pelletization and the pressed part is referred to as compact. The quality of the product made by pelletizing is recognized to be dependent upon many factors such as intrinsic material properties, particulate material properties, nature of applied load, and die geometry. Many pelletization defects such as lamination, capping, and stress cracking etc. are caused by anisotropic compaction of the particulate material. It is further recognized by researchers that the anisotropic compaction, among other factors, is attributable to non-uniform pre-compaction fill-density of the particulate material in the die. Filling or the deposition of powders in confined spaces such as dies is the required first step in the process of manufacturing pressed parts/products. Since errors are usually compounded in any manufacturing process, it stands to reason that ensuring a pre-compaction uniform particulate deposition in the die or mold would be an effective method of ensuring and enhancing quality of the pressed compacts.
Even though researchers have studied the effect of filling methods on fundamental particulate properties and load distribution in large storage systems, there exists a significant lack of qualitative and quantitative analysis of the process of die filling in relation to a particulate material's pre-compaction density distribution within the die volume. The ability to measure the in-situ, pre-compaction fill density distribution within the particulate mass inside the die volume is of paramount importance to the objectives of research work and no study is believed to exist where researchers have carried out such an in-situ density distribution of particulates in dies or molds. Five potential techniques currently available are radiogaging, x-ray CAT scanning, Process Tomography, vacuum assisted epoxy impregnation and magnetic resonance imaging (MRI), A pros and cons analysis involved weighing the financial viability verse the technical limitations of the different techniques found that none of these techniques were a feasible option. For example, a sample of wheat flour was tested for its spatial density distribution in a CAT scan machine. While the results were promising, the costs involved were considered unacceptable on account of the fact that the CAT scan machine is very expensive to own or rent. Even if unlimited funds were available to do CAT scanning, it would simply be impossible to test certain powders that would cause high attenuation of incident x-rays so as to render them undetectable by the CAT scan sensors. Similarly, while a MRI machine can do extensive imaging of the human body, test results on a sample of wheat flour tested in a MRI machine were found to be negative. Even if a MRI machine could be coupled to detect the presence of a certain molecule in a given powder, the prohibitive costs of MRI machines (even costlier than CAT scan machines) would preclude their use. The radio-gaging and process tomography techniques involve similar high ownership or rental costs. The vacuum assisted epoxy impregnation technique is an inexpensive technique, but its use in achieving the objectives of this study were considered unacceptable for two reasons. The first reason being that percolation effects of epoxy through the powder mass may cause particle dislocation. The second reason being that there could be potential chemical reactions between the epoxy and particulate material.
It is an object of the present invention to provide a test apparatus to determine spatial, in-situ fill density distribution of a material in confined spaces.
It is an object of the present invention to provide a test apparatus to allow the determination of the effect of filling methods, rate of fill, die cross-section and die size (aspect ratio) on the spatial fill density distribution of a material within a die volume.